Fukushima Feldspar (福島長石)
A standard material in Glazecalc's library: its oxide analysis, unity contribution and hazards.
What it is
- Kind
- Feldspars and stones
- Formula
- SiO₂ 65.4%, Al₂O₃ 19.53%, Fe₂O₃ 0.09%, CaO 0.49%, MgO 0.1%, Na₂O 3.77%, K₂O 10.76%, LOI 0.18%
- Also called
- 福島長石, Fukushima feldspar
- Sold in
- JP
- Source
- 佐賀県陶磁器原料株式会社 (Arita): 釉薬原料の化学分析表, the supplier's typical analysis of what it sells (undated; read 2026-10-19)
A typical analysis from one supplier in Arita: check it against your own supplier's. Japan's usual potash feldspar, sold in several grades (極上, 特級, 特選, 亀甲) that differ: a sample sold as 福島長石 that the Shiga ceramic research institute analysed had 72.1% SiO₂ and 8.2% K₂O.
Oxide analysis and unity formula
Glazecalc has the analysis of Fukushima Feldspar (福島長石) as weight percent of the raw material. The unity contribution is the moles of each oxide in the amount of Fukushima Feldspar (福島長石) that holds 1.0 mole of flux, which is how Glazecalc adds it into a recipe's unity formula.
| Oxide | Weight % | Unity contribution |
|---|---|---|
| SiO₂ | 65.4 | 5.843 |
| Al₂O₃ | 19.53 | 1.028 |
| Fe₂O₃ | 0.09 | 0.003 |
| CaO | 0.49 | 0.047 |
| MgO | 0.1 | 0.013 |
| Na₂O | 3.77 | 0.327 |
| K₂O | 10.76 | 0.613 |
- Equivalent weight
- 536.83
- Fired weight
- 535.87
- Loss on ignition
- 0.18%
The equivalent weight is the grams of Fukushima Feldspar (福島長石) that hold 1.0 mole of flux. The fired weight is what is left of that after firing.
Hazards and safety
Hazards: Contains crystalline silica; avoid breathing the dust.
Use it in a recipe
Add Fukushima Feldspar (福島長石) to a recipe in the Glazecalc calculator to see what it does to a glaze's unity formula.